Short Answer:

Metamorphic rock is a type of rock that forms when existing igneous or sedimentary rocks undergo high pressure and heat deep within the Earth. This process, called metamorphism, changes the rock’s texture, structure, and mineral composition without melting it. Metamorphic rocks are classified into foliated (layered) and non-foliated (non-layered) types based on their appearance.

Metamorphic rock forms under pressure and heat when tectonic movements, deep burial, or magma intrusion increase the temperature and compress the rock. Over time, these conditions cause minerals to rearrange, forming new, harder rocks such as marble, slate, gneiss, and schist. These rocks are widely used in construction, flooring, and sculptures.

Detailed Explanation:

Metamorphic Rock

Metamorphic rocks are formed when existing rocks are subjected to extreme heat, pressure, or mineral changes without melting. This process occurs deep underground, where tectonic forces and high temperatures cause rocks to recrystallize and develop new textures.

There are two main types of metamorphic rocks based on their structure:

1. Foliated Metamorphic Rocks (Layered Appearance):
   • Form due to directed pressure, creating layers or bands.
   • Examples: Slate, schist, gneiss.
2. Non-Foliated Metamorphic Rocks (No Layers):
   • Form under uniform pressure, resulting in a dense structure.
   • Examples: Marble, quartzite.

These rocks are commonly found in mountain ranges, deep underground, and near magma intrusions.

How Metamorphic Rock Forms Under Pressure and Heat

Metamorphic rocks form through intense pressure and high temperatures, which cause changes in their mineral structure. This transformation happens in the following stages:

1. Exposure to Heat:
   • When magma intrudes into surrounding rock, the heat causes chemical changes.
   • Example: Limestone turns into marble due to high temperatures.
2. Pressure from Tectonic Movements:
   • When tectonic plates collide, rocks get compressed and transformed.
   • Example: Shale turns into slate, then into schist, and finally into gneiss.
3. Recrystallization of Minerals:
   • Minerals rearrange into new structures, making the rock harder and more durable.
   • Example: Quartz grains in sandstone fuse together to form quartzite.

This process takes millions of years and occurs in deep Earth environments where temperatures exceed 200°C and pressure builds up due to geological forces.

Uses of Metamorphic Rocks in Civil Engineering

• Marble – Used in sculptures, flooring, and monuments.
• Slate – Used for roofing, flooring, and blackboards.
• Gneiss – Used in construction as crushed stone.
• Quartzite – Used in road construction and countertops.

Metamorphic rocks are highly durable, resistant to weathering, and aesthetically valuable, making them essential in construction and architecture.

Conclusion

Metamorphic rock forms when existing rocks undergo high pressure and heat without melting. This process, known as metamorphism, changes their structure, making them harder and more compact. These rocks are widely used in construction, artistic works, and geological studies due to their strength and beauty.